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Measuring and weighing without contact

12 February 2018

At the Hannover Messe 2018 trade fair, Festo is presenting among other things a concept for contact-free weighing and measuring.

Highly pure, sterile processes are a key challenge for the industrial production of tomorrow – especially in food processing and the pharmaceuticals and medical technology industries, but also in the electronics sector. To keep manufacturing processes as free from contamination as possible, the workpieces and the workroom should be separated from each other. This can be achieved with superconductor technology. At the Hannover Messe 2018 trade fair, Festo is presenting among other things a concept for contact-free weighing and measuring.

Particularly in cleanrooms, surfaces must be sealed, and be able to be easily and effectively cleaned and disinfected. The items of apparatus present the biggest challenge here: from test tubes to distillation columns, they are introduced from the outside and can bring in germs. Moreover, the contact surfaces on their bases develop minute cracks that are difficult to keep clean. The use of levitation technology based on magnetic fields – for example superconductor technology – can dispense with such problems in future.

SupraSensor: measuring and weighing without contact

One of the many possibilities is shown by the SupraSensor, an exhibit to be presented by Festo at the Hannover Messe 2018 trade fair. It demonstrates the function of a contactless balance, which could be used for example on sterile workbenches in biological or chemical analytics. This concept allows various physical quantities, such as weight, density, viscosity or temperature, to be measured using a force-based measuring system.

An easy-to-clean laboratory environment

“In a laboratory environment, workplace surfaces remain clear of apparatus and can therefore be effectively and easily cleaned, since everything except the carrier for the item to be weighed can be screened from the surroundings,” explains Georg Berner, Head of Strategic Corporate Development, Group Holding Festo and Project Coordinator for the SupraMotion concepts. “Only the weighing pan carrying the item hovers over the table top – without the danger of cross-contamination via the workplace surface or tools.” The entire weighing apparatus can be decoupled from the surroundings without vibration by means of a frame. If the pan is not needed, it can be removed and the entire working space of the sterile workbench becomes available.

Separation of work area and apparatus

The SupraSensor exhibit consists of a hermetically sealed liquid-filled tube positioned over a high-precision balance, to which a cryostat with a superconductor is fixed. In the tube is a float with a permanent magnet on the underside, which is contactlessly coupled to the superconductor on the outside and thus also to the balance. This is made possible by a special characteristic of superconductors: they can hold magnets in suspension at a fixed distance when cooled to a certain temperature.

The SupraSensor operates on the flotation principle: the more buoyancy that is given to the body with the magnet, the lower its specific weight, as is demonstrated for example by bubbles of air that accumulate on the float and force it upwards. This is indicated by the balance, since it has a contact-free connection with the body via the superconductor. Since the density and thus also the buoyancy of a liquid change depending on its composition, this principle can be used to determine in what concentration further soluble substances are added. This can be compared to flotation in sea water: the more salt it contains, the greater its buoyancy and the less deeply a body is submerged in it. The SupraSensor exhibit thus demonstrates how a workroom and laboratory equipment, including sensors, can be coupled to each other without contact despite spatial separation.

Applications in medical technology

In addition to purely measuring and weighing, this technology offers numerous further possibilities such as analytical determination of density or viscosity, precise metering or the surveillance of reactive or biological processes. “The possibility of handling objects without contact and thus completely free of contamination is of great interest above all in medical technology. Since no friction arises, measurements are not falsified and are absolutely precise,” says Dr. Frank Jacob, Head of the MedLab Project Unit at Festo. “The concept of the superconductive balance is now being realised in close cooperation with one of our customers as a prototype. It shows how we can construct easy-to-clean weighing devices in future and integrate them into automated systems in combination with our drive technology.”

The technology is very robust and stable in terms of both space and time: the levitation function, which is intrinsic to the material, does not require any regulation technology and remains stable over long periods, even if the power supply is interrupted.

Further new concepts for superconductivity

Festo has now been developing superconductor technology for application in automation technology for ten years. At the Hannover Messe 2018 trade fair, further exhibits in addition to the SupraSensor concept will be showcased that extend the wide range of applications of this technology once more.

Superconductors are materials that can store the field of a permanent magnet at a defined distance below a certain temperature. With this effect, objects can be held in position and moved free of contact. The levitation gap remains stable even beyond walls. Thanks to its restoring forces, the superconductive magnetic bearing components autonomously return to their stored positions, even if one of them is temporarily removed – without the need for external regulation technology.